tabcontainer control giving error 1 could not be set on property 'ActiveTabIndex' and dropdown list control in update panel does not perform any action and gives error in asp.net with c#

Question

hi iam using asp.net with c#
iam using tab ccontainer of ajax control , inside this iam using update panel and drop down list but drop down list not performing any action
and when you select any item from drop down list it gives error

error
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Invalid postback or callback argument. Event validation is enabled using <pages enableEventValidation="true"/> in configuration or <%@ Page EnableEventValidation="true" %> in a page. For security purposes, this feature verifies that arguments to postback or callback events originate from the server control that originally rendered them. If the data is valid and expected, use the ClientScriptManager.RegisterForEventValidation method in order to register the postback or callback data for validation

and tab container while designing not showing controls and shows 1 could not be set on property 'ActiveTabIndex'

Amit Choudhary · Answer

for your second problem of ActiveTabIndex you should go through my article on Enhancing the functionality of Ajax Tab Control it'll surely help you Please Don't forget to mark Do you like this post if it helps.

Amit Choudhary · Answer

hi friend there is two solution for this problem. 1. set EnableEventValidation=false attribute of aspx tag . 2. Or if you have some code written inside the page_load event if not necessary to call the code at postback then if(!Page.IsPostBack) { // you complete code inside page_load event will go here } Any of the above method will solve your problem.. but choose second one carefully it may change your behavior of program while postback. Please Don't forget to mark Do you like this post if it helps.

Dipa Ahuja · Answer

There may me some mistake in your code.. you have to write your code to find the mistake